1. Field of the Invention
The present invention relates to an addition curing type fluorine-containing curable composition which forms a gel type cured product from which bleeding is extremely limited and which displays excellent chemical resistance and solvent resistance following curing, and which is ideally suited for applications such as potting materials, sealing or encapsulating materials and coating materials used with electrical or electronic components.
2. Description of the Prior Art
Gel type cured products of silicone rubbers offer superior electrical and thermal insulation and display stable electrical characteristics and flexibility, and are consequently widely used as the potting and sealing or encapsulating materials for electrical and electronic components, and as coating materials for protecting control circuit elements such as power transistors, ICs and condensers from external thermal or mechanical faults.
A representative example of a silicone rubber composition for forming this type of gel type cured product is an addition curing type organopolysiloxane composition. This type of addition curing type organopolysiloxane composition comprises, for example, an organopolysiloxane with vinyl groups bonded to silicon atoms, and an organohydrogenpolysiloxane with hydrogen atoms bonded to silicon atoms, and yields a silicone gel through a cross-linking reaction in the presence of a platinum-based catalyst (refer to Japanese Laid-open publication (kokai) No. 56-143241 (JP56-143241A), No. 62-3959 (JP62-3959A), No. 63-35655 (JP63-35655A) and No. 63-33475 (JP63-33475A)).
Furthermore, fluorosilicone gel compositions comprising an organopolysiloxane with trifluoropropyl groups are also known (refer to Japanese Laid-open publication (kokai) No. 7-324165 (JP7-324165A)).
However, the silicone gels obtained from these types of addition curing type organopolysiloxane compositions are susceptible to swelling and degradation by chemicals such as strong bases and strong acids, as well as solvents such as toluene, alcohol and gasoline, and maintaining the performance of the gels has proven difficult.
In order to resolve this problem, a fluorine-containing gel composition comprising a linear compound having a bivalent perfluoropolyether group in its backbone chain and having two alkenyl groups per molecule as a main constituent, and also comprising an organohydrogenpolysiloxane with hydrogen atoms bonded to silicon atoms, and a platinum-based catalyst, together with a fluorine-containing gel type cured product produced from such a composition, have been proposed (refer to Japanese Laid-open publication (kokai) No. 11-116685 (JP11-116685A)).
However, when a gel of this description is used as a protective material, stress such as pressure fluctuation, and heat history cause a free oil component to bleed from the gel, resulting in contamination of the electrical or electronic component. This contamination can cause the electrical or electronic component to either exhibit substandard performance or even fail to operate. Furthermore following curing of the gel, in cases where additional materials are then used, the gel can cause deterioration in the adhesion and leakage. Accordingly, a gel composition with only a very small bleeding component, but which produces a gel type cured product, has been keenly sought.